Egocentric anchoring-and-adjustment of social knowledge in the hippocampal formation

Recent work suggests the hippocampal formation(HF) assimilates relational social knowledge similar to how it transforms egocentric spatial cues into map-like representations. Yet whether hippocampal map-like representations of social knowledge still represent lingering egocentric biases is unclear. We test if a prominent egocentric bias involving an implicit reliance on self-knowledge when rating others, anchoring-and-adjustment, is present when the relative attributes of different social entities are assimilated by the HF. Participants provided likelihood ratings of partaking in everyday activities for themselves, fictitious individuals, and familiar social groups. Adapting a functional neuroimaging task from Kaplan and Friston, participants then learned a stranger’s preference for an activity relative to one of the fictitious individuals and inferred how the stranger’s preference related to the groups’ preferences. Egocentric anchoring-and-adjustment was present when participants rated the other entities. Isolating the neural representation of egocentric anchoring-and-adjustment when flexibly comparing different social entities, the HF and dorsomedial prefrontal cortex(dmPFC) represented group-self rating discrepancy. Furthermore, the HF also reflected how well group preferences were remembered, where memory for group preferences correlates with task performance. We found the HF selectively represented group identity over other learned entities, confirming that the HF was primarily engaged by social comparisons in a more ample frame of reference. Taken together, these results imply that self-knowledge influences how the HF assimilates map-like knowledge about others.